Aqueous coating compositions for adhering light-sensitive emulsion to polyester film

ABSTRACT

An aqueous coating composition for adhering various types of layers to polyester sheet or film surfaces, the aqueous coating composition comprising a vinylidene chloride terpolymer, gelatin, and a copolymer of ethylene and vinyl acetate.

United States Patent Inventors Thomas .1. Dolce Scotch Plains;

Donald L. McCabe, Rahway, both of NJ. 35,288

May 6, 1970 Division of Ser. No. 637,348,

May 10, 1967, Pat. No. 3,539,476

Oct. 26, 1971 Celanese Corporation New York, N.Y.

Appl. No. Filed Patented Assignee AQUEOUS COATING COMPOSITIONS FORADHERING LIGHT-SENSITIVE EMULSION TO POLYESTER FILM 5 Claims, NoDrawings U.S. Cl 96/87 R, 117/34, 117/138.8 F, 117/161 UT Int. Cl G03cl/80 Field of Search 96/87;

117/34, 138.8 F, 161 UT [56] References Cited UNITED STATES PATENTS2,397,866 4/1946 McQueen 96/84 2,627,088 2/1953 Alles et a1.... 264/1342,779,684 l/l957 Alles 117/7 2,943,937 7/1960 Nadeau et a1 96/872,976,168 3/1961 Thompson et a1. 117/34 3,081,198 3/1963 Miller 117/1553,143,421 8/1964 Nadeau et al... 96/87 3,443,950 5/1969 Rawlins 96/87Primary ExaminerRonald H. Smith Attorneys-Thomas .1. Morgan, Linn l.Grim and Richard A.

Lucey ABSTRACT: An aqueous coating composition for adhering varioustypes of layers to polyester sheet or film surfaces, the aqueous coatingcomposition comprising'a vinylidene chloride terpolymer, gelatin, and acopolymer of ethylene and vinyl acetate.

BACKGROUND OF THE INVENTION i This invention is a divisional applicationof U.S. Pat. appli-; cation, Ser. No. 637,348, filed on May 10, 1967,now Pat. NO.; 3,539,476.

The present invention relates to an improved aqueous coating compositionfor polyester sheet or film. More particularly, the present inventionrelates to polyester sheet or film having a resinous coating on at leastone surface thereof, and still more particularly to a polyester filmbase wherein the resinous coating functions as an im oved anchoringsubstratum or subbing layer between the rrlm base and alight-sensitive,f water-permeable colloid layer or emulsion disposedthereon.

It is known that high molecular weight linear polyesters can be formedinto sheets having many desirable physical properties which make themattractive for use as photographic film, bases. This is particularlytrue for highly polymeric ethylene glycol-terephthalic acid polyesters.However, polyesters of this class are very hydrophobic, and in order tosecure adhe-. sion to them of a normal type of hydrophilic,light-sensitive;

emulsion layer, it is necessary to provide one or more inter-{ mediateanchoring layers, so-called subbing or substratumf layers. While variouscompositions and combinations of layersi have been proposed and used forthis purpose, such as a com-; position comprising a terpolymer ofvinylidene chloride, none have proven entirely satisfactory in actualcommercial practice. For example, the use of synthetic polymer subbingcom-! positions usually requires a second subbing thereover of a gelatincomposition prior to the application of the light-sensitive emulsionlayer. But even with 2 the double subbing. technique, the finalphotographic film elements usually show some skidding and spontaneousstripping of the emulsion layer after processing and drying operations.

In addition, the surface of the subbing layer or layers used heretoforehas been rough, thereby detrimentally affecting the ultimatephotographic quality of the film element.

SUMMARY OF THE INVENTION Accordingly, the primary object of the presentinvention is} to provide an improved coating composition for adhering a;light-sensitive emulsion layer to a polyester film base. Other! objectswill appear hereinafter.

In accordance with the present invention there is providedj an aqueouscoating composition comprising a. from about 5 to about 40 weightpercent of a vinylidene, chloride terpolymer,

b. from about 2 to about 35 weight percent of a copolymer. of ethyleneand vinyl acetate, and

c. from about 0.5 to about 15 weight percent of gelatin. l The aqueouscoating composition has a maximum solids con-. tent of about 65 weightpercent.

Preferably, the coating composition consists essentially of a. fromabout 24 to about 32 weight percent of the terpolymer,

b. from about 6 to about 14 weight percent of the ethylen copolymer,

c. from about I to about 5 weight percent of gelatin, and

d. the remainder water and additives conventionally used by thoseskilled in the art such as dispersants, antifoams and the like.

DESCRIPTION OF THE PREFERRED EMBODIMENT It has been found that the abovethree component subbing layer adheres firmly to polyester sheet or filmbase. In addition, when the three component layer is over coated with agelatin layer and/or a light-sensitive emulsion layer, the film elementthus obtained retains all of the desirable physical properties of thepolyester film base with none of the aboye-rnentioned disadvantages ofemulsion skidding and stripping which occurs with related prior artphotographic elements. Moreover, the three component subbing layerresults in a smooth surface such that the photographic quality of thefinal film element is not detrimentally affected.

The vinylidene chloride terpolymer which is used in the presentinvention is the well known terpolymer of vinylidene chloride, anacrylic ester, preferably acrylonitrile, and itaconic acid, the initialrelative proportions of the monomers in the polymerization reactionmixture being within the following ranges:

The useful acrylic esters which are nonnally employed in the 5production of the terpolymer are the alkyl esters of acrylic andlmethacrylic acids, the alkyl group having from one to l8caribon atoms,e.g., methyl methacrylate, ethyl methacrylate, butyl methacrylate,octamethacrylate, n-dodecyl methacryglate, n-octadecyl methacrylate,methylacrylate, ethylacrylate and propylacrylate. The tenn acrylicesters is also meant to include vinyl chloride, acylonitrile andmethacrylonitrile.

The above monomers may be copolymerized to yield the terpolymer by anyof the methods well known to those skilled in the art, for example, asset forth in Alles et al. U.S. Pat. No.

The ethylene-vinyl acetate copolymers useful in the present inventionare thermoplastic solids containing about 1 to 30 percent combinedethylene and correspondingly about 70 to 99 percent of combined vinylacetate. Copolymers containing about 5to 2 percent ethylene and about topercent vinyl acetate are particularly desirable.

Preferably, the ethylene-vinyl acetate copolymer is prepared and used inthe form of an aqueous emulsion. Suitable copolymers of this type haverecently been introduced commercially under the Aircoflex brand of AirReduc- ;tion Corporation, and have the following typical properties.

Alrcoflex I00 I Torsion modulus at 25 C. I Gehrnan Flexibility Tester1,000 p.s.i.

Sofiness at 25" C. Penetrometer 3.3 mm. 1 Calendered gloss", aspercentage of 75 reflectance 67% Ultimate Tensile Strength 650 p.s.i.Ultimate Elongation l, l 50% Weight-average molecular weight Greaterthan one million .LLDQMQQ "Determined on clay coatings containing 20parts binder solids for each I00 parts clay.

"*Values obtained on an lnstron teslerat 72 F. and 50% RH. and at across- J sLUmhsam nuepressure. However, lower or higher temperatures andpressures may be used, although they are not necessary. The coatingcomposition may be filtered, if so desired, in order to enhance theconsistency of the resulting composition.

The aqueous coating composition may be deposited on one.

or more sides of the polyester support or film base by any of theconventional methods used in the manufacture of photographic elements,e.g., by immersion of the surfaces of the film into a solution of thecoating material, spraying, beading, or coating from a hopper providedwith a doctor blade, etc. Preferably, both sides of the polyester filmor sheet are coated. In this manner, one side may then be overcoatedwith a photographic emulsion, and to eliminate any tendency to curl, theother side overcoated with a gelatin composition containing nolight-sensitive components, but which may contain, if desired,antistatic agents, filter dyes, antihalation agents, and the like. Theaqueous coating composition may be applied to the polyester support orfilm base either before or after it has been stretched or oriented, forexample, as set forth in Alles et al. U.S. Pat. No. 2,627,088.

If desired, more than one layer of the coating composition may beapplied. The thickness of the resulting coating of the three componentcomposition of the present invention, whether applied as one ormorelayers, may vary over a fairly wide range, e.g., 0.05 mil to 1.0 milor more. In general, however, coatings of from 0.1 to 0.2 mil will bemost useful.

The resulting coated support or film base is dried for a period of timein the range of from about 5 seconds to about minutes, and preferablyfrom about 30 seconds to about 2 kminutes at a temperature in the rangeof from about 75 to about 200 C., and preferably from about 100 to about150 C.

After the three component subbing layer has dried, a gelatin layerand/or any of the well known light-sensitive emulsion layers may becoated thereover and dried.

Any of the light-sensitive materials used by those skilled in the artmay be coated onto the three component anchoring or subbing layer. Inaddition to light-sensitive silver salts, such as silver chloride,silver bromide, silver chloride-bromide, silver chloride-iodide andsimilar mixtures, there may be utilized bichromated hydrophiliccolloids, e.g., albumin, gelatin, gum arabic, polyvinyl alcohols, orglue. The light-sensitive layers, of course, are applied in the absenceof actinic radiations. Immobile color formers, dye intermediates or dyesmay be present in such layers. Other materials include light-sensitiveiron salts and diazonium compounds with or without coupling components.

Suitable polyester sheet or film materials which may be used in thepresent invention may be composed of any polyester of a dicarboxylicacid and a dihydric alcohol of the type described in Carothers U.S. Pat.No. 2,071,250, or may be composed of any of the high-melting, usuallymicrocrystalline, cold-drawing linear, highly polymerized esters ofterephthalic acid and glycols of the series HO(CH ),,OH, where n is aninteger within the range of 2to 10, as described in whinfield et al.U.S. Pat. No. 2,465,319.

Moreover, the polyesters from which the film or support is made need notconsist solely of glycol units since some of the glycols react to formpolyglycols, and small percentages of units from such polyglycols may bepresent. For instance, when ethylene glycol is a reactant, the polyestermay contain from 1 to percent or more of units from diethylene glycol(i.e., Cl-l,Cl-l OCl-l,Cl-l Ounits). Also when a mixture of glycols andpolyglycol is used, e.g., ethylene glycol and diethylene glycol, thecopolymers may contain a substantial proportion of oxyethylene units.

Preferably, the polyester sheet or film to which the aqueous coatingcomposition is applied is crystallizable polyethylene terephthalate, andmore preferably polyester which has been heat treated as set forth inAlles U.S. Pat. No. 2,779.684.

The-polyester film may contain pigments or dyes to color it any desiredcolor. When the film is to be used as photographic film base for X-rayfilm, it may be tinted green or blue. The three component subbing layermay be similarly tinted and may contain an antistatic material. Filledopaque polyester film or polyester films coated with carbon to make themopaque may also be used.

If desired the subbing or anchoring composition of the present inventionmay be used on bases made of paper and hydrophobic materials such ashydrophobic cellulose carboxylic acid ester, including celluloseacetate, cellulose acetate butyrate, cellulose nitrate; a superpolymer,for example, a superpolyamide (nylon), a polyvinyl chloride, and thelike.

This invention is additionally illustrated by the following examples,wherein all percentages or parts are on a weight basis unless otherwiseindicated:

EXAMPLE 1 A vinylidene chloride-acrylonitrile-itaconic acid terpolymerwas made by admixing the following constituents in a reaction vessel:

Grams vinylidene chloride 600.0 Acrylonitrile 52.7 ltaconic acid 6.6Water 989.0 Ammonium persulfate 0.70 Sodium metabisulfite 0.35 Sodiumlauryl sulfate (Duponol ME) 55.4

The reaction vessel was heated to about 34 C. and the contents stirreduntil all of the vinylidene chloride was consumed, which is indicated bycessation of reflux. The time required to consume the vinylidenechloride was about three hours. The resulting terpolymer emulsion wasthen cooled and filtered.

Fifteen hundred grams of the aqueous terpolymer emulsion was then mixedwith 500 grams of a 10 percent by weight aqueous gelatin solution andthe resulting mixture filtered.

Eighteen hundred grams of the terpolymer-gelatin composition was thenmixed with 500grams of an ethylene-vinyl acetate copolymer emulsion(Aircoflex having a 50 percent by weight solids content to yield anaqueous coating com- The above composition was then coated onto apolyethylene terephthalate film and the coating dried at 100 C. for 2minutes. After drying, three component subbing layer was subjected tothe Scotch Tape test. The adhesion of the subbing layer to the polyesterfilm was excellent as none of the subbing was removed or pulled away bythe Scotch Tape. In addition, the surface of the subbing layer was quitesmooth.

A gelatin solution (10 percent by weight gelatin) was applied as anovercoating to a polyester film having a subbing layer as describedabove. The gelatin overcoating was dried at F. for 5 minutes. Theadhesion of the gelatin layer was measured by the "Scotch Tape test andfound to be excellent.

When a light-sensitive emulsion layer is applied on top of the threecomponent subbing layer, either with or without an intermediate gelatinlayer, the light-sensitive emulsion layer is not removed by the ScotchTape" test. In addition, the' final photographic film element does notshow any skidding or spontaneous stripping after final processing anddrying operations.

EXAMPLE ll Ninety parts of the vinylidene chloride terpolymercomposition described in example I was mixed with parts of an aqueoussolution of gelatin (10 percent by weight gelatin). The resultingterpolymer-gelatin composition, containing 36 percent terpolymer and 1percent gelatin, was then coated onto a polyethylene terephthalate filmand the coated film dried at'l00 C. for Zminutes. The resulting gelatinterpolymer subbing layer surface was quite rough.

A gelatin layer was then added as an overcoat as in example I, dried,and the -Scotch Tape" test applied. The gelatin layer pulled away fromthe subbing layer.

EXAMPLE lll A vinylidene chloride terpolymer emulsion similar to thatdescribed in example 'l, containing 40 percent by weight solids, wascoated on to a polyethylene terephthalate film and dried at 100 C. for 2minutes. The resulting terpolymer subbing layer surface was quite rough.An aqueous gelatin solution was then applied as an overcoating as inexample I. After drying, the adhesion of the gelatin layer was measuredby the Scotch Tape" test and was found to be very poor as it pulled awaywith the tape.

The principle, preferred embodiment, and mode of operation of thepresent invention have been described in the foregoing specification.However, it should be understood that the invention which is intended tobe protected herein, may be practiced otherwise than as describedwithout departing from the scope of the appended claims.

What is claimed is:

1. In a method for adhering a light-sensitive emulsion layer to at leastone surface of a polyester film, the improvement which comprises coatingsaid polyester film surface with at least one subbing layer of anaqueous coating composition comprising a. from about 5 to about 40weight percent of a terpolymer of vinylidene chloride, acrylic ester,and itaconic acid,

b. from about 2 to about 35 weightpercent of a copolymer of ethylene andvinyl acetate, and

c. from about 0.5 to about 15 weight percent of gelatin, said aqueouscoating composition having a solids content in the range of from about 5to about 65 weight percent.

2. The method of claim 1, wherein the aqueous coating compositioncomprises from about 24 to about 32 weight percent of the terpolymer,from about 6 to about 14 weight percent of the ethylene copolymer, fromabout 1 to about 5 weight percent of gelatin, and the solids content ofthe aqueous coating composition is in the range of from about 20 toabout 60 weight percent.

3. A polyester film which has been coated on at least one surface withan aqueous coating composition comprising a. from about 5 to about 40weight percent of a terpolymer of vinylidene chloride, acrylic ester anditaconic acid,

b. from about 2 to about 35 weight percent of a copolymer of ethyleneand vinyl acetate, and

c. from about 0.5 to about 15 weight percent of gelatin, the

total solids content of the aqueous coating composition being in therange of from about 5 to about 65 weight percent.

4. The polyester film of claim 3, wherein the aqueous coatingcomposition comprises from about 24 to about 32 weight percent of theterpolymer, from about 6 to about 14 weight percent of the ethylenecopolymer, from about I to about 5 weight percent of gelatin, and thesolids content of the aqueous coating composition is in the range offrom about 20 to about 60 weight percent.

5. A photographic element comprising at least one silver halide emulsionlayer superimposed upon a polyester film support which has been coatedwith an aqueous coating composition comprising in the range of fromabout 24 to about 32 weight percent of a terpolymer of vinylidenechloride, an acrylic ester and itaconic acid, from about 6 to about 14weight percent of a copolymer of ethylene and vinyl acetate, from about1 to about 5 weight percent of gelatin, and the solids content of theaqueous composition is in the range of from about 20 to about 60 weightpercent.

Patent No. 3 5l5 5 6 l Dated October 26. 1971 IYWEHCQT( 5) gnomes J.Dglge and Donald L. McCabe It is certifltxl tllit err: appears in thabove-identified patent and that said Le d r m1: Iataat at: he rebyCDIISC'. to as shown below: r- In the Specification at Column 2, line 41"about 5 to 2 percent' should read about 5 to 20 percent Signed andsealed this 28th day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. The method of claim 1, wherein the aqueous coating compositioncomprises from about 24 to about 32 weight percent of the terpolymer,from about 6 to about 14 weight percent of the ethylene copolymer, fromabout 1 to about 5 weight percent of gelatin, and the solids content ofthe aqueous coating Composition is in the range of from about 20 toabout 60 weight percent.
 3. A polyester film which has been coated on atleast one surface with an aqueous coating composition comprising a. fromabout 5 to about 40 weight percent of a terpolymer of vinylidenechloride, acrylic ester and itaconic acid, b. from about 2 to about 35weight percent of a copolymer of ethylene and vinyl acetate, and c. fromabout 0.5 to about 15 weight percent of gelatin, the total solidscontent of the aqueous coating composition being in the range of fromabout 5 to about 65 weight percent.
 4. The polyester film of claim 3,wherein the aqueous coating composition comprises from about 24 to about32 weight percent of the terpolymer, from about 6 to about 14 weightpercent of the ethylene copolymer, from about 1 to about 5 weightpercent of gelatin, and the solids content of the aqueous coatingcomposition is in the range of from about 20 to about 60 weight percent.5. A photographic element comprising at least one silver halide emulsionlayer superimposed upon a polyester film support which has been coatedwith an aqueous coating composition comprising in the range of fromabout 24 to about 32 weight percent of a terpolymer of vinylidenechloride, an acrylic ester and itaconic acid, from about 6 to about 14weight percent of a copolymer of ethylene and vinyl acetate, from about1 to about 5 weight percent of gelatin, and the solids content of theaqueous composition is in the range of from about 20 to about 60 weightpercent.